This invention relates to doors for mine stoppings, and more particularly to so-called "man doors" for use in masonry and metal mine stoppings.
So-called "stoppings" are widely used in mines to stop off flow of air in passages in the mines, a "stopping" generally being a masonry (e.g., concrete block) or metal wall installed at the entrance of a passage to block flow of air therethrough. It is often desired that such stoppings be provided with a door, which is referred to as a "man door", for occasional access to the blocked-off passage. A serious problem is encountered, however, in providing a door for a stopping because heaving and shifting of the stopping, as often occurs, results in the parallelograming of the door frame, which may result in jamming and buckling of the door and leakage of air through the stopping.
This invention is in the same field as and may be regarded as representing an improvement upon the doors for a mine stopping disclosed in U.S. Pat. Nos. 4,082,331 and 4,118,894.